1. Why do Illustrator, Fireworks and InDesign (these are the ones I have checked) open with floating panels, tabs and windows, even in full screen mode... but Photoshop opens nicely in windowed mode with all the panels, tabs and windows fixed?

2. In full screen mode the left ruler is hidden behind the tools panel?! Why?!

Read up on workspaces and how to use and modify them. That's all it comes down to. There's no difference between the programs other than using different defaults, but it's perfectly possible to have them all with neatly docked workspaces. That also solves the ruler problem.